Updated version of https://phab.comm.dev/D5518 (in new stack).
The web app should behave as the native app:
- when selecting someone in the chat composer who isn't a friend, and when nobody else is selected, the web app should exit search and create a 1-1 thread with this user
- should display alert if you try to add a non-friend when you have already selected some users
- should display alert on blocked users